Dental calculus, or tartar as it is sometimes called, is a deposit which forms on the surfaces of the teeth of humans and some lower animals at the gingival margin. Supragingival calculus appears principally in the areas near the orifices of the salivary ducts; e.g., on the ligual surfaces of the lower anterior teeth and on the buccal surfaces of the upper first and second molars, and on the distal surfaces of the posterior molars.
Mature calculus consists of an inorganic portion which is largely calcium phosphate arranged in a hydroxyapatite crystal lattice structure similar to bone, enamel and dentine. An organic portion is also present and consists of desquamated epithelial cells, leukocytes, salivary sediment, food debris and various types of microorganisms.
As the mature calculus develops, it becomes visibly white or yellowish in color unless stained or discolored by some extraneous agent. This is undesirable from an aesthetic standpoint.
A wide variety of chemical and biological agents have been suggested in the art to retard calculus formation or to remove calculus after it is formed. Mechanical removal of this material periodically by the dentist is, of course, routine dental office procedure.
The chemical approach to calculus inhibition generally involves chelation of calcium ion and/or crystal growth inhibition which prevents the calculus from forming and/or breaks down mature calculus by removing calcium.
The prior art discloses a number of chelating agents for this purpose. British Patent 490,384, Feb. 15, 1937, discloses oral compositions containing ethylenediaminetetraacetic acid, nitrilotriacetic acid and related compounds as anticalculus agents. U.S. Pat. No. 3,678,154, July 18, 1972 to Widder et al. discloses oral compositions containing certain polyphosphonates and fluoride. U.S. Pat. No. 3,737,533, June 5, 1973 to Francis discloses oral compositions containing certain carbonyl diphosphonates.
In addition to the above references, the prior art discloses dentifrices and mouthwashes containing soluble pyrophosphate salts which have been included for a variety of purposes but not all for anticalculus purposes. Included among such references are U.S. Pat. No. 2,941,926, June 21, 1960 to Salzmann et al. which discloses dental powders containing chlorophyll and pyrophosphate salts. U.S. Pat. No. 3,137,632, June 16, 1964 to Schiraldi discloses toothpastes containing pyrophosphate salts. U.S. Pat. Nos. 3,927,201 and 202, Dec. 16, 1975 to Baines et al. and Harvey et al., respectively, discloses toothpastes which utilize soluble pyrophosphates as abrasives. U.S. Pat. Nos. 4,244,931, Jan. 13, 1981 and 4,247,526, Jan. 27, 1981 to Jarvis et al. disclose pyrophosphate salts in dicalcium phosphate systems. Jap. Patent Application Disclosure No. 4945-1974 discloses soluble pyrophosphates in a variety of dentifrice systems. U.S. Pat. No. 4,333,551, Apr. 6, 1982 to Parran discloses tetraalkali metal salts in mouthwash compositions. U.S. Pat. No. 4,515,772, May 7, 1985 to Parran, et al., discloses compositions containing soluble pyrophosphate salts as anticalculus agents. U.S. Pat. No. 4,627,977, Dec. 9, 1986 to Gaffar et al., discloses oral compositions containing mixtures of polyphosphates and linear, anionic polymers as anticalculus agents.
In addition to the use of the above mentioned materials the use of certain acrylic acid polymers and other agents have also been disclosed for use as anticalculus agents. Included among such agents are polyelectrolytes such as copolymers of maleic anhydride and ethylene disclosed in U.S. Pat. No. 3,429,963, Feb. 25, 1969 to Shedlovsky. Shedlovsky also discloses polyacrylic acid having an average molecular weight of 1500 and greater. Another reference disclosing polyacrylic acids in oral compositions is South African Patent 720,898, Sept. 12, 1972 which discloses such acids having a molecular weight in the range of 2,000 to 4,000,000 for use as a membrane to prevent the elution from teeth of previously applied agents. U.S. Pat. No. 3,956,480, May 11, 1976 to Gaffar discloses complexes of anionic polymers (e.g. acrylic acid) and a cationic therapeutic agent (e.g., chlorhexidine) as anticalculus agents. Strontium chelates have also been disclosed for use in oral compositions, particularly in the enhancement of fluoride uptake.
Phosphocitrate has been widely disclosed in the medical literature for a variety of purposes. One very widely reported use is for the prevention of stone formation in the kidneys or urinary tract. Among references disclosing this use are Howard, J. E., "Studies on Urinary Stone Formation a Saga of Clinical Investigation", Johns Hopkins Medical Journal 139 (6), 1976, pages 239-252; Gimenez, et al., "Phosphocitrate Prevents Phosphate Induced Loss of Renal Function in Experimental Aremia", Clinical Research, 29 (2), 1981, page 539A; and Tew et al., "The Effects of Phosphocitrate on Experimentally Induced Nephro Calcinosis", Kidney International, 19 (1) 1981, page 117.
Another area where phosphocitrate has been disclosed to have utility is in the area of prevention of hydroxyapatite formation in bone and cartilage. A reference disclosing this use is Reddi et al., "Influence of Phosphocitrate, a Potent Inhibition of Hydroxylapatite Crystal Growth, on Mineralization of Cartilage and Bone", Biochem. Biophys. Res. Commun., 97 (1), pages 154-159.
Although there have been a number of approaches disclosed for combatting calculus, there is still the desire and need to develop additional products possessing that property. The prior art while disclosing the use of phosphocitrate for a variety of purposes does not suggest its use for reducing calculus through the topical application to dental enamel in the mouths of humans or lower animals.
It is an object of the present invention to provide compositions which deliver an anticalculus benefit.
It is a further object of the present invention to produce an effective anticalculus product using a phosphocitrate material.
It is still a further object of the present invention to provide anticalculus products which are cosmetically acceptable and do not inhibit remineralization of the teeth.
It is still a further object of the present invention to provide effective methods for combating calculus.
These and other objects will become more clear from the detailed description which follows.
All percentages and ratios used herein are by weight and all measurements are made at 25.degree. C. unless otherwise specified.